The present invention relates to a halogen lamp assembly for a substrate processing chamber.
Substrate processing chambers, in which a substrate such as a semiconductor wafer or display is processed, often use halogen lamps for heating the substrate or chamber walls. Halogen lamps are incandescent lamps that typically have tungsten filaments in a halogen gas environment encapsulated in a quartz glass envelope. The envelope is constricted at the base of the lamp to form a pinch seal end about metal connectors that pass current to the filament. These lamps give off heat that is used to anneal a layer of material on the substrate, as for example, in a rapid thermal processing (RTP) chamber; or to decompose a gas to form a layer on a substrate as in an epitaxial chamber. The halogen lamps can generate the infrared heat energy quickly, controllably, and with uniform coverage, and thus they are useful for rapidly heating the substrate.
However, the heat emitted by the halogen lamp can cause failure of critical regions of the lamp and thereby reduce the lifetime of the lamp. One region of the lamp that is particularly susceptible to failure is the pinch seal end. The pinch seal end is exposed to even higher temperatures by the additional resistive heat generated from the passage of the electrical current through the connectors passing through this region. The high operating temperatures can cause the glass to metal seal to fail due to stresses arising from a mismatch in thermal coefficients of expansion of the glass, metal, and glass to metal sealing material. The heat can also cause partial oxidation or other deterioration of the metal connectors. Thus, a halogen lamp with an expected lamp life of about 2000 hours or greater for a maximum operating temperature of 300° C. at the pinch seal end, has a much shorter lifetime of about 1000 hours when the operating temperature in the pinch seal end is 350° C., and a lifetime of only about 250 hours when the operating temperature is 400° C.
Thus it is desirable to have a halogen lamp assembly with a heat sink that is capable of reducing the operating temperature of the lamp. It is also desirable to keep the pinched seal region temperatures below critical levels to reduce premature failure of the lamp. It is also desirable to remove the heat generated by the lamp during its operation without complex cooling equipment.